1. Field of the Invention
The present invention relates to an apparatus for an information recording medium, such as an optical disc, an optical card and an opto-magnetic disc. In the apparatus according to the invention, the information recording medium contained in a cassette case is set up to record, erase and reproduce information on and from the information recording medium.
2. Prior Art Statement
Hitherto, there have been suggested various kinds of apparatus for an opto-magnetic disc; in the apparatus a field coil for recording, erasing and reproducing information is arranged so as to face the surface of the opto-magnetic disc. In such apparatus, when an electric current is supplied to the field coil, the temperature of the opto-magnetic disc is increased by the heat generation of the field coil. In such case, it would be impossible to record, erase and reproduce information on and from the disc correctly. Therefore, the apparatus is arranged such that an outside air is taken inside thereof, for instance, by means of a fan in order to cool the opto-magnetic disc; or arranged such that the number of turns of the field coil is increased to make a value of the electric current in the field coil small in order to decrease the heat generation in the field coil.
However, in the construction of the conventional apparatus such that the opto-magnetic disc is cooled by taking outside air into the apparatus, there is a drawback namely that dust, which comes from the outside, adheres to the opto-magnetic disc or optical members constituting an optical head; and thus information cannot be recorded, erased and reproduced in a correct and stable manner due to the reason that the amount of light is decreased by the dust adhering to the optical members. On the other hand, in the construction such that the heat generation is depressed by increasing the number of turns of the field coil, there is a drawback in that the size of the field coil becomes large so that the apparatus as a whole also becomes large and heavy.
In order to solve these drawbacks, in Japanese Patent Preliminarily Publication No. 1-171144, there is disclosed an improved apparatus, in which under the condition that an opto-magnetic disc is loaded on the apparatus, a fan is arranged on a spindle motor, which is for rotating the opto-magnetic disc, via the opto-magnetic disc and a magnet. An air current is generated in the apparatus by the fan, which is rotated integrally with the spindle motor, so that the field coil is cooled.
However, in the construction that the fan is arranged on the spindle motor, since too much load is generated in the spindle motor, the rotation accuracy is decreased and then information cannot be recorded, erased and reproduced in a correct and stable manner. Further, since the fan is arranged on the spindle motor so as to be integrally rotated with the spindle motor when the opto-magnetic disc has been loaded on the apparatus, the construction of the apparatus becomes complex and the cost for manufacturing the apparatus increases.
Further, in the apparatus for information recording medium, generally, a disc-type information recording medium, which is contained in the cassette case, is inserted and ejected by an auto loading/ejecting mechanism with respect to a deck, which comprises the spindle motor, an optical pick-up means for recording and reproducing information on and from the disc, and a driving means for driving the optical pick-up means in a radius direction of the disc.
In such apparatus, the optical pick up means is constituted by fine optical members; and thus the pick up means is easily affected by a shock. Therefore, when the apparatus is, for instance, transported, or in other words, when information is not recorded, erased and reproduced in the apparatus, it is necessary to lock the pick up means in order to prevent that the pick up means is affected by vibration caused by the transportation thereof. In Japanese Patent Preliminarily Publication No. 1-253885, there is disclosed an apparatus which comprises a locking means which serves to lock the pick up means in response to the movement of the auto loading/ejecting mechanism. In the conventional apparatus, the locking means is urged against the pick up means to lock it when the disc is ejected from the apparatus.
However, in the conventional locking mechanism, it is arranged that a locking arm and a locking plate, which constitutes the looking mechanism, are urged against the pick up means at outside of a pair of slide shafts, by which the pick up means is supported to be movable in a radius direction of the disc. Therefore, a rotating deviation affects to the portion where the pick up means is urged against the locking mechanism. The rotating deviation causes a non-desired stress on the slide shafts or slide bearing provided in the pick up means, so that the pick up means could not be moved smoothly and the durability of the slide shafts and the bearings therefore are aggravated.
In a case that the pick up means is locked by such means that the pick up means is urged against a stopper, made by elastic material such as rubber, by the locking mechanism, when the pick up means has been locked for a long time, the elastic material of the stopper would be transformed and then the function of the stopper is decreased, or the elastic material of the stopper would be sometimes adhered to the pick up means, and thus the pick up means could not be driven. In a case that the pick up means is locked without being urged against the stopper, in order to solve the problem, it is necessary to make an accuracy for controlling the stop position of the pick up means high, so that the cost for manufacturing the apparatus becomes high.
Furthermore, in the apparatus for information recording medium, the information recording medium is contained in a cassette case in order to prevent the effect of dust. When the apparatus is loaded with the cassette case, which contains the recording medium, the cassette case is firstly held on a cassette case holder and transported in a horizontal direction and then transported in a vertical direction to be set up on a turn table, by which the information recording medium in rotated to record and/or reproduce information thereon and/or therefrom. On the cassette holder, a field unit is generally fixed to be integrally transported therewith.
However, there is a drawback in that the weight of the cassette holder becomes heavy due to the weight of the field unit, and therefore, the load generated on the cassette case holder and on a driving means for the cassette case holder is increased, when the cassette case holder is transported in the horizontal and vertical directions.